1. Field of the Invention
For various reasons, both economic and technical, individual circuit card modules are frequently of quite large size, exceeding 20 cm. in length and width. With the increasing density of logic functions per component, even one circuit board can perform a large number of complicated functions. This being the case, it frequently arises that optional functions available for various devices cannot be conveniently placed on one or more standard size cards, in that only a fraction of the area of one or more cards may be filled. This of course is wasteful of circuit card and backpanel space.
Accordingly, it is desirable that half-size or other fractional size cards be usable in such devices. This requires a free-standing card guide which may be placed between the standard guides in specified locations to permit the use of under-width cards. Because of the inability to foresee various changes in operation of the device that may be belatedly added in the field, it is desirable that these intermediate guides be easily attached and detached.
Such intermediate card guides should have a substantial percentage of the mechanical strength and rigidity of permanent guides and yet, if necessary, be locatable in adjacent card positions, to provide maximum flexibility in selection of these positions for cards with particular functions. Because of the relatively close spacing between adjacent card positions, little area is available for bracing the bases of the intermediate guides.
2. Description of the Prior Art
Although no specific art is known which addresses this problem, there are a variety of obvious techniques which immediately come to mind. One might be a guide having opposite facing slots with feet projecting at right angles thereto and made rigid with fastening screws passing through holes therein and bolting to the connector panel. A variation might find these feet interlocking in above and below fashion so as to allow adjacent feet on adjacent guides to be fastened by a single screw. Such an approach does not allow a single guide adjacent another to be easily attached or detached. Holes may be provided in the back panel which receive the end of the guide and are retained therein with a snap-locking arrangement or with the screws inserted on the wiring side of a back panel. Alternatively, a bracing framework designed to fit in the spaces between adjacent cards can provide the stability needed for a guide having an insufficiently rigid attachment to a back panel. It would be possible to make a very rigid intermediate card guide by ganging several together and bolting them to the back panel as a unit. However, this latter approach decreases flexibility in choice of location for individual small-width cards.